Question

a normal population has a mean 31 and standard deviation 7. what is the probability that a randomly chosen value will be greater than 18?

Answer 1

0.969

Explanation:

use the z-score formula to convert the values.

z = (X - υ) / σ

where X is the test statistic, υ is the mean, σ is the standard deviation.

z = (18 - 31) / 7

= -1.857

area in z-score table (this is area to left of <18) is 0.0314.

P(>18) = 1 - 0.0314 = 0.969